I get excellent results with these:
Verbatim DataLifePlus Crystal Super AZO CD-R 52x (MCC type 3)
Tried writing speeds: 48x, 40x, 32x
My NEC 3500 writes these discs equally well at speeds 32-48x (haven't tried anything slower). I don't know about long-time stabilty as I have only had these discs for a month, but they have a fairly scratch resistant top (i.e. "Crystal").
Here's a PlexTools C1/C2 scan performed in a Plextor PX-712A drive at 48x speed; the disc was written at 40x with firmware 2.18 LD_V2 beta4:
Note: PlexTools doesn't directly support scanning at higher than 24x, but it can be tricked into doing so by externally changing the drive's reading speed.
EDIT: These discs are "Made in China" and were bought in Germany.